Laser Speckle Flowgraph Reveals Dynamic Characteristics and Clinical Relevance of Choroidal Watershed and Peripapillary Hypoperfusion Zones

The hemodynamic characteristics of the choroidal watershed zone (CWZ) have not been fully quantified. We aimed to characterize the blood flow and pulsatility within the choroidal hypoperfusion zone (CHZ) and investigate its relationship with adjacent optic nerve head (ONH) perfusion in healthy eyes, using laser speckle flowgraphy (LSFG). Blood flow and pulsatile waveform metrics were compared within and outside the CHZ and in optic nerve head (ONH) sectors in 100 healthy participants. Two patients with non-arteritic anterior ischemic optic neuropathy (NAION) were also reviewed as the illustrative cohort. In the illustrative cohort, the CHZ in LSFG color maps showed qualitative spatial correlation to areas of delayed choroidal filling on fluorescein angiography. In the main cohort, average flow was lower by 44.3 ± 15.4% and the average, minimum, and maximum blood flow and pulsatility measures were significantly lower (P < 0.0001 for key indices) within the CHZ than outside. Time to peak systolic blood flow was delayed (P = 0.028). The temporal-to-nasal flow ratio in the ONH was significantly reduced when the CHZ was more temporally located relative to the optic nerve center (P = 0.0015). In conclusion, the tissue located within the CWZ is more vulnerable to drops in ocular perfusion pressure.